A heat sensitive paper is known which employs sublimable materials such as sublimable dyes. The heat sensitive paper comprises a record sheet coated with a developer and a transfer sheet which faces the record sheet and which is coated with a dye. The dyes on the transfer sheet are sublimed or evaporated by heat onto the record sheet and reacted with the developer on the record sheet to obtain a color-developed image.
The most important color of such heat sensitive paper is black. However, no black dyes which are sublimed by using a small amount of heat energy have been proposed. Japanese Patent Publication (unexamined) No. 220788/1983 discloses a process wherein a sublimable basic dye is transferred to a pretreated sheet to develop a color. The developed color of the disclosed process is restricted to magenta, cyan and yellow, because no black dyes which can be easily sublimed by a heat energy of a conventional thermal head are known.
In order to the above mentioned defects, the present inventors have proposed heat sensitive paper in Japanese Patent Applications 154879/1984 and 17257/1985. The heat sensitive paper develops a good black color, but exhibits defects in oil and light resistance.